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Overview

The FHWA released a memorandum requiring all new bridge designs to be LRFD-based after October 1, 2007. This directive was the culmination of more than a decade of effort by Modjeski and Masters in leading a team of experts in the development of the AASHTO LRFD Bridge Design Specifications. In line with this directive, the FHWA has set a date of October 1, 2010 after which all new bridges are to be rated using the LRFR method rather than the LFR method. However, the choice of load rating method for existing bridges may affect the transportation of goods and services over the nation’s highways by restricting routes that were previously unrestricted. The bridge community needed additional research and comparisons of the LRFR and LFR ratings to be sure that the rating process maintained an acceptable level of reliability without unnecessary restrictions on commerce.

Modjeski and Masters supported a team led by Michael Baker, Jr. to recommend refinements to the LRFR methods in the AASHTO Manual for Bridge Evaluation. Our technical experts worked with the team to explain changes in truck restrictions and to develop a comprehensive database of rating comparisons. Our problem solvers are utilizing the database to identify differences in ratings and aid in developing proposed refinements. The team continues to refine the analysis and is developing a summary report with recommendations. The report will be presented to the review panel in the near future.

Modjeski and Masters continues its long-term relationship with the NCHRP and LRFD through this and other continuing assignments including: NCHRP 12-83, Calibration of LRFD Concrete Bridge Design Specifications for Serviceability, NCHRP 20-7, Task 270, Application of AASHTO LRFD Specifications to Design of Sound Barriers; FHWA’s Manual for the Design, Construction, and Maintenance of Orthotropic Steel Bridges; and our ongoing maintenance of the LRFD specifications, which we began in 1996. Improving the art of bridge building through innovative research – another hallmark of Modjeski and Masters.

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Tasks Performed

Research and Code Development

Bridge Geometry

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Testimonial

Modjeski and Masters continues its relationship with the NCHRP through this and other continuing assignments including NCHRP 12-83, Calibration of LRFD Concrete Bridge Design Specifications for Serviceability and NCHRP 20-7, Task 270, Application of AASHTO LRFD Specifications to Design of Sound Barriers.